Knowledge of local temperatures during the compression of air/fuel-mixtures is of major interest when modeling engine combustion. Especially in ultra-lean burning modern engines using stratified load and exhaust gas recirculation inhomogeneous mixing takes place and causes temperature inhomogeneities. Thus, two-dimensional temperature imaging techniques have to be applied to provide the necessary information about endgas conditions. It is well known that laser induced fluorescence (LIF) of ketones like acetone and 3-pentanone is susceptible to temperature, depending on the excitation wavelength. This is mainly due to a shift of the absorption band with temperature. Detailed studies of the photophysical properties of 3-pentanone in heated high-pressure cells provide the background which enables quantitative evaluation of tracer-LIF intensities. With quasi-simultaneous two-line excitation 3-pentanone-LIF can be used for measuring temperature distributions even in systems where the tracers are not homogeneously mixed. The inferred temperture in turn can be used to correct the individual images of tracer-LIF for further quantifying fuel distribution measurements.